1. Field of the Invention
This invention relates to a contact shutter mechanism in an IC socket, in which a contact included in a socket body is opened and closed by vertical movement of a contact shutter member.
2. Brief Description of the Prior Art
In Japanese Patent Early Laid-open Publication No. Sho 62-160676, a socket body includes a contact shutter member supported in an elevated position by a contact. The contact is displaced backward by pushing down the contact shutter member against the resiliency of the contact to form a non-contacted state relative to an IC contact and to bring an IC loading portion into a released state so that an IC package can be loaded and removed. A pressing portion for exerting a backward displacement force on the contact is formed in a plane at a right angles to the contact, the backward displacement being obtainable by vertically pushing down a projecting end of a rear portion of the contact with the right angle plane.
The contact is displaced forward by its own restoring force and contacted with an upper surface of the terminal of the IC package, supported on a sink-and-float platform of the socket body by the restoring force. At the same time, the contact renders a upward force to the contact pushing portion to hold the contact shutter member in the elevated position so as to be ready for the next non-contact operation.
Since the above-mentioned prior art is designed such that the IC terminal is held down from above of the contact to maintain the IC terminal in the IC socket body, the arrangement for holding the IC package in the IC socket can be simplified. In addition, the contact can be displaced backward simply by pushing down the contact shutter member to cancel the holding of the IC package so that the IC package can be immediately removed or loaded again. Accordingly, it has the advantage in that it can be easily automated by using a robot. Moreover, as a stable contact can be obtained and reliability is excellent, this prior art is widely used.
While the prior art has the above-mentioned advantages, it also has the main shortcoming in that, as the contact is displaced backward in the direction generally perpendicular to the vertical direction by a push-down force in the vertical direction of the contact shutter member, the push-down force is apt to become excessively large.
In a general IC socket of, for example, 40 pins, a push-down force of about 1.6 kg. is required, and because of this reason, the number of IC sockets which can be pushed down at one time by using a robot, and the efficiency in IC measuring operations is lowered. This tendency becomes more and more significant as the number of poles and the density is increased. How to overcome this problem is now a big issue.
In Japanese Patent Early Laid-open Publication No. Sho 62-93964, it is proposed to form the contact pushing portion with an inclined surface in order to cope with the above problem. According to this proposal, although the push-down force can be reduced, the push-down stroke becomes two times or more compared with the prior art, in accordance with the angle of inclination, and not only can the contact not rapidly respond but such a new problem as insufficient dilation results.
The present invention has been accomplished in order to obviate the above-mentioned problems.